DESCRIPTION: The ability to perform high-throughput, high-purity, multi-parametric cell sorting is extremely important for many biomedical studies and clinical applications. In the past few decades, fluorescence-activated cell sorters have become the gold standard technique in the field. However, current cell sorters suffer from an inability to maintain cell integrity during the cell- sorting process. Conventional cell-sorting processes are reported to significantly reduce cell viability and function (30-70% reduction) for many fragile or sensitive cells such as neurons, stem cells, liver cells, dendritic cells, sperm cells, and even neutrophils from healthy individual. In addition, our recent preliminary results indicate that gene expression can be significantly altered during the cell-sorting process, even for robust cells (such as HeLa cells). These drawbacks significantly limit the usefulness of cell sorters in many biomedical studies and clinical applications and have created many unmet needs. For example, human induced pluripotent stem (iPS) cells have opened a new field for modeling human diseases using human cells directly. They can be extremely useful for drug screening and personalized medicine. However, today it is still impossible to use cell sorters or any other existing methods to isolate undifferentiated iPS cells in a high-throughput, high-purity, and high-cell-integrity manner. This unmet need has significantly hindered progress in stem cell research and therapy. Our objective is to address these unmet needs by demonstrating standing surface acoustic wave (SSAW) based, high-cell-integrity sorters. When compared to conventional sorters, the proposed SSAW cell sorter is substantially smaller and less expensive, and is expected to significantly improve post-sorting cell viability, function, and gene expression for both fragile and robust cells. In particular, we will (1) develop a SSAW-based flow cytometer that achieves sheathless, multi-color, high-throughput single-cell analysis; (2) demonstrate a high-throughput, single-cell deflecting unit using focused interdigital transducers (f-IDTs); (3) establish a fully integrated, SSAW-based cell sorter system proven with human blood samples to outperform a state-of-the-art cell sorter; and (4) demonstrate sorting of induced pluripotent stem (iPS) cells with maintained cell integrity. With unprecedented capabilities to maintain cell integrity, even for fragile cells, our proposed SSAW-based cell sorter will not only become a more compact, affordable, and easy-to-maintain replacement to the existing cell sorters, but also fill many unmet needs in both fundamental biomedical research and clinical diagnosis and therapeutics.